Method of making hollow articles



Patented Oct. 24, I939 PATENT OFFICE METHOD OF MAKING HOLLOW ARTICLES William Scrimgeour, Washington, D. 0., assignor to The National City Bank of Cleveland, Cleveland, Ohio, as trustee Application January 27, 1936, Serial No. 61,108

3 Claims.

This invention relates to methods of making hollow articles, particularly poppet valves for internal combustion engines, by forging operations.

The method which is claimed in my copending 5'? application, Serial No. 13,348, filed March 27,

1935, includes the punching of a solid steel cylinder to form a tubular blank having a rounded end wall, the working down of the tubular portion of the blank to form an elongated stem of 10 small diameter, and the die pressing of the end portion of the blank to shape the same into a valve head having a diameter substantially larger than that of the original steel cylinder and of the tubular shell.

15 The presentinvention relates particularly to the formation of valves from blanks produced with dies of the type shown in Fig. 6d of my prior application.

An object of the invention is to provide im- 2 proved and economical methods of forging one piece hollow articles such as poppet valves, from blanks of shorter length and less diameter than the corresponding dimensions of the finished article. Further objects are to provide methods of forming hollow valves by punching a solid steel blank to form a tubular shell, the punching or a subsequent stamping operation effecting a lateral flow of metal at the end of the blank to form the end wall and rim portion of the valve 30 head approximately to final form and dimensions, and then working down the remainder of the tubular shell to form an elongated stem of small diameter.

These and other objects and advantages of the 35 invention will be apparent from the following specification when taken with the accompanying drawing in which:

Fig, 1 is a fragmentary sectional view through dies and a punch which may be used in per- 40 forming the first operation on the blank, a

punched blank being shown in the dies;

Fig. 2 is a perspective view of a blank prior to the punching operation;

Figs. 3 and 4 are somewhat diagrammatic views 45 illustrating successive rolling operations in the formation of the elongated valve stem;

Figs. 5 and 6 are sectional views through dies and a press, respectively, illustrating an alternative method of forming a tubular blank;

50 Fig. '7 is a view, similar to Fig. 1, illustrating dies for forming valves with slightly domed heads; and

Figs. 8 and 9 are fragmentary side elevations of finished valves having, respectively, flat and 55 domed heads.

In Fig. 1, the reference numeral l identifies a die block which has a bore 2 extending through the same, the lower end of the bore being flared outwardly to a diameter equal to that of the head of the valve which is to be formed. The die 5' block rests upon a die member 3 which, if desired, may have a small recess 4 in its upper plane surface to form a lug on the valve head. The movable head 5 of the press carries a punch 6 Which is forced into a short cylindrical steel 10 blank '7, see Fig. 2, to form the tubular blank l'a which is shown in Fig. l.

The lower end of the punch 6 is rounded, and the walls of the punch and of the bore 2 have a slight taper to facilitate the separation of the punch from the blank 1a, and the removal of the blank through the bottom of the die 2, after the displacement of the die member 3. The diameter of blank 1 is somewhat less than that of bore 2, and the steel blank is heated to a high temperature before it is placed in the die. It is to be noted that the outer wall and rim portion of the valve head are formed to the desired size and shape by the punching operation of this invention.

The tubular section of the blank la is forge-d, for example by a rolling operation, to form an elongated small diameter stem integral with the valve head. As indicated in Fig. 3, the blank la may be inverted and temporarily supported on a mandrel 3 between a plurality of shaping rolls 9, 9' which are rotated and forced towards each other to exert pressure radially of the tubular section of the blank. Only two rolls are shown in the diagrammatic views, Figs. 3 and 4, but it is preferable to use three rolls, with two rolls 9 rotated by an appropriate power source and roll 9 free to rotate with the blank as the latter is turned by the driven rolls.

The rolls 9, 9' transform the tubular shell or blank 1a into the blank lb by forming the portion adjacent the end wall to the desired flaring shape of the rear surface of the valve head, and also reduce the adjacent metal to the approximate stem diameter. Blank lb is then placed between rolls l0, l0 which have elongated cylindrical portions for rolling down the remainder of the blank to form the long small diameter stem. The blank 10 may then be finished by machining and/or grinding operations.

As shown in Figs, 5 and 6, the end wall and rim section of the valve head may be formed in two steps by punching a cylindrical steel blank in die members la, 3a to form a tubular blank Ha having a thick end wall, and pressing the blank to effect a lateral flow of the metal to form the head section. Blank Ila is placed over a plunger I I in a die block I2, and die head I3 is forced down upon the blank Ila to displace metal radially into the flared upper end of the die block I2. Blank Ill) and plunger II are then removed from the die I2, and the blank is stripped from the plunger. The lower face of the die head I3 may be plane or, as shown, it may be recessed to impart a slight dome or concave form to the valve head. The tubular section of blank IIb is then rolled or swaged to form the elongated stem. Whether the lateral flow of metal takes place during the punching or in a subsequent operation, the outer diameter of the tubular shell is approximately that of the original blank but the end wall section is of substantially larger.

diameter to serve as the head end of the finished valve.

A domed shape may be imparted to a blank I by substituting a die member 3' having a slightly concave upper surface, Fig. '7, for the flat surfaced die member 3 of Fig. 1.

Finished hollow valves Hi, M of the flat top and domed top types, respectively, are shown in Figs. 8 and 9. Seat engaging surfaces I5 are machined and ground and, when the lugs I6 are used, they are slotted to receive a tool for rotating the valve for grinding operations.

Reference is made to my prior application for a more detailed description of appropriate apparatus for performing the described punching and rolling operations. This invention is, in common withthat claimed in the prior application, very economical in that there is but little waste of the expensive steel which is customarily used for hollow valves, and it has the further advantage that the full diameter head is formed on the tubular blank during or immediately after the punching operation,

It is to be understood that there is some lati-- tude in the particular design of the dies and the rolls, and that the form of the blank at different intermediate stages may therefore vary somewhat from the blanks illustrated herein.

I claim:

1. The process of forming a hollow poppet valve which comprises punching a solid cylindrical blank to form a tubular shell having an outer diameter approximating that of the blank and a thick end wall, compressing the end. wall between forming dies to effect a radial outward flow of metal in the end wall, thereby to form a thin end Wall section having an enlarged diameter, the inner diameter of the tubular shell adjacent the end wall'remaining substantially the same during the compressing step of the process, and working down the tubular shell to form an elongated small diameter stem.

2. The process of forming a valve as defined in claim 1, wherein the tubular shell is collapsed and worked down by a rolling operation to form a substantially solidvalve stem and a closed cavity in proximity to said end wall.

3. The process of forming a hollow' poppet valve which includes providing a metal blank having a hollow tubular portion and a thick end wall, inserting a removable plunger into the blank against the thick end wall thereof, radially outwardly extruding a portion of the metal in the thick end wall byaxially compressing theend Wall against the plunger, the inner diameter of the tubular portion adjacent the end wall remaining substantially the same during the extruding step of the process, slidably withdrawing the plunger from the, blank, and working down the hollow tubular portion to reduce the diameter thereof to provide a valve stem.

WIILIAM SCRIMGEOUR. 

